In the next grant year we propose to investigate further: (1) Cell compartments involved in assembly of ferritin; (2) Heart alloferritins in two strains of rats; (3) Immunoradiometric assay of rat tissue ferritins and their protein subunits. In these investigations, we propose to use (a) rat organs and tissues, including hearts and livers, (b) rat hepatoma cells cultured in vitro. The following methods will be applied: cell fractionation, radioimmunoassays and immunoradiometric assays, biochemical assays, analytical centrifugation, light and electron microscopy. BIBLIOGRAPHIC REFERENCES: Lee, S.S.C. and Richter, G.W., The monomers and oligomers of ferritin and apoferritin: Association and dissociation. Biochemistry 15: 65-70 (1976); Richter, G.W. Evolution of cytopllsmic fibrillar bodies induced by lead in rat and mouse kidneys. Relation to clusters of ferritin. Am. J. Pathol. 83: 135-148 (1976).